From 177c53d943368fc97644ebc0a250dc8e2d124250 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 28 Feb 2014 13:39:05 +0100 Subject: [PATCH] stop_machine: Fix^2 race between stop_two_cpus() and stop_cpus() We must use smp_call_function_single(.wait=1) for the irq_cpu_stop_queue_work() to ensure the queueing is actually done under stop_cpus_lock. Without this we could have dropped the lock by the time we do the queueing and get the race we tried to fix. Fixes: 7053ea1a34fa ("stop_machine: Fix race between stop_two_cpus() and stop_cpus()") Signed-off-by: Peter Zijlstra Cc: Prarit Bhargava Cc: Rik van Riel Cc: Mel Gorman Cc: Christoph Hellwig Cc: Andrew Morton Link: http://lkml.kernel.org/r/20140228123905.GK3104@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- kernel/stop_machine.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 84571e09c907..01fbae5b97b7 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -293,7 +293,7 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void * */ smp_call_function_single(min(cpu1, cpu2), &irq_cpu_stop_queue_work, - &call_args, 0); + &call_args, 1); lg_local_unlock(&stop_cpus_lock); preempt_enable();